Ninja Turtles less teenaged in this two-fisted relaunch of their franchise

The “Teenage Mutant Ninja Turtles” earn a Michael Bay-produced 3-D re-boot that spares no expense in special effects and spares no decibel in the volume that is the soundtrack to all their new mayhem.

These digitally animated super-sized turtles have real-world presence and weight, stumping onto the scene like teenagers who haven’t learned to do anything quietly. Their brawls with their trigger-happy foes from the Foot Clan are a blur of body blows and bullets. Their wisecracks are up-to-date, their love of pizza unabated.

Their human friend is a fluff-friendly TV reporter played by Megan Fox. So yeah, Bay gave this production the full “Transformers” treatment. It’s entirely too violent, but teenaged turtles armed with ninja swords, knives and nunchucks have always been violent, from their origins in the 1980s comic books to assorted TV series and the films of the ’90s and an animated flop of 2007.

The new film, directed by Jonathan Liebesman (“Battle Los Angeles”) quickly and gracefully handles the back story – a lab experiment and a fire – and puts shapely TV reporter April O’Neil (Fox) on their case right from the start.

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The Foot Clan, led by the mysterious megalomaniac Shredder (voiced by Danny Woodburn) is trying to take over New York. But these masked vigilantes keep foiling their plans.

April starts to piece together a puzzle that points to her own past, the man her scientist father was in business with (William Fichtner) and the “mutagen” and other chemicals they were toying with.

The heroes are masked ninjas, mutant turtles who grew huge, learned English and trained in martial arts with the inscrutable rat, Splinter (Tony Shalhoub). Michelangelo, Raphael, Donatello and Leonardo only occasionally act like teenagers, usually in their banter.

April cannot convince her boss (Whoopi Goldberg) that she’s not crazy. And her on-the-make cameraman (Will Arnett, toned down and not nearly funny enough) is also a hard sell regarding these “heroes on a half-shell.”

The animated rat has a much bigger role in this film than is usual for this series, and the animators give Splinter a few cute tricks to pull off with his tale, as well as an Asian martial arts master’s long, thin goatee.

The action beats are bigger and better than they’ve ever been in a Ninja Turtle film – brawls, shootouts, a snowy car-and-truck chase with big explosions and whatnot.

But in between those scenes is an awful lot of chatter and exposition. For a film that aims younger (save for the die-hards who grew up with this franchise), that’s deadly dull.

And Fox, emoting as if her “comeback” depended on this, plays it all straight, which tends to rob the film of needed playfulness. The turtle brothers are somewhat less distinct as character “types” – the tech nerd, the angry rebel, the boy on the make, the leader. Among the voice actors playing the Project Renaissance turtle brothers, only Johnny Knoxville stands out.

So even though they “did justice” to this beloved franchise, there’s nothing here than won’t be forgotten by the time you’ve gotten home – AFTER you stopped for pizza on the way.